A global satellite observation of phytoplankton taxonomic groups over the past two decades.

Marine phytoplankton fuel the oceanic biotic chain, determine the carbon sequestration levels, and are crucial for the global carbon cycle and climate change. In the present study, we show a near-two-decadal (2002-2022) spatiotemporal distribution of global phytoplankton abundance, proxy as dominant phytoplankton taxonomic groups (PTGs), with a newly developed remote sensing model. Globally, six chief PTGs, namely chlorophytes (~26%), diatoms (~24%), haptophytes (~15%), cryptophytes (~10%), cyanobacteria (~8%), and dinoflagellates (~3%), explain most of the variation (~86%) in phytoplankton assemblages. Spatially, diatoms generally dominate high latitudes, marginal seas, and coastal upwelling zones, whereas chlorophytes and haptophytes control the open oceans. Satellite observations reveal a gentle multi-annual trend of the PTGs in the major oceans, indicative of roughly "unchanged" conditions on the total biomass or compositions of the phytoplankton community. Jointly, "changed" status applies to a short-term (seasonal) timescale: (1) Fluctuations of PTGs exhibit different amplitudes among different subregions, together with a general rule-more intense vibration in the Northern Hemisphere and polar oceans than other zones; (2) diatoms and haptophytes vary more dramatically than other PTGs in a global-scale scope. These findings provide a clear picture of the global phytoplankton community composition and can improve our understanding of their state and further analysis of marine biological processes.

Seasonal dynamics of phytoplankton in the northern part of Suez Gulf, Egypt.

This study was conducted to evaluate the seasonal variability of phytoplankton in the northern part of the Gulf of Suez (Suez Bay), considering the contribution of physicochemical parameters of bay water in shaping the dynamics, and eutrophication assessment. Water and phytoplankton samples were collected seasonally at nine stations in the Suez Bay during the period from the winter to autumn of 2012. A total of 423 phytoplankton species were identified, comprised mainly of 224 diatoms, 127 dinoflagellates, 33 cyanophytes, 20 chlorophytes, and 9 euglenophytes; the rest of the species (10 species) belong to other six groups. Of these, 28 species were potentially harmful. The total phytoplankton abundance exhibits a significant seasonal variation, with the autumn being the most fertile season, followed by the winter due to the proliferation of diatom species Thalassionema nitzschioides and Proboscia alata f. gracillima, respectively. While the seasonal species richness indicates that the winter attained the highest number of species, followed by summer. Generally, the major diatom genera were Chaetoceros (16 species), Navicula (15 species), Nitzschia (15 species), and Amphora (14 species), while dinoflagellates were principally composed of the genera Protoperidinium (34 species), and Tripos (26 species). Water temperature, pH, salinity, nitrate, and nitrite were the most important explanatory parameters in regard to phytoplankton abundance and chlorophyll a concentration. In addition, the phytoplankton stability exhibited a significant positive relationship with the mean values of dissolved oxygen and biological oxygen demand and the variability of salinity and phosphate, while a negative relationship was observed with ammonia and nitrite and the variability of nitrate. Based on the trophic index (TRIX), the bay water was classified as mesotrophic (moderately polluted) for almost the entire year except in the autumn as it turned eutrophic. The results explored the potential importance of the environmental heterogeneity in the bay as a key structuring mechanism of phytoplankton abundance and biomass, influenced by anthropogenic activities.

Response of the phytoplankton community to seasonal and spatial environmental conditions in the Haldia port ecosystem located in the tropical Hooghly River estuary.

The phytoplankton community structure exhibits seasonal and spatial variations in response to the environmental conditions, which aids in understanding the ecosystem's health. Given this, four samplings were conducted between October 2013 to April 2015, encompassing the monsoon, post-monsoon, and pre-monsoon seasons, from the Haldia port ecosystem of India. The samples were collected from the flowing estuary and an extended semi-enclosed dock. We hypothesized that the seasonal phytoplankton community (diversity, abundance, and carbon biomass) response will differ based on the environmental and hydrographical characteristics of the study site. Picophytoplankton and nano-microphytoplankton dominated the phytoplankton community in terms of numbers and biomass, respectively. Bacillariophytes dominated the nano-microphytoplankton abundance and total biomass, except during the monsoon when Dinophytes contributed (inner-zone). The dominance of Bacillariophytes and Chlorophytes in the outer-zone with picophytoplankton and Dinophytes in the inner-zone indicated group-specific hydrographic preferences that supported the hypothesis. The positive correlation of the picophytoplankton abundance (pre-monsoon) with Secchi disc depth and the negative correlation of diatoms (post-monsoon) with temperature signify the seasonal role of light and temperature, respectively. The highest nano-microphytoplankton species diversity (Shannon-Wiener's index) during the pre-monsoon (inner-zone) with more rare species indicated the probable influence of stable waters with increased water transparency. However, the community was unevenly distributed in the estuary due to the high abundance of the diatom, Aulacoseira granulata. Although harmful algal blooms were not detected, the higher temperature and nutrient concentrations could have favoured potentially harmful species (Pseudonitzschia delicatissima, Dinophysis acuta) during the monsoon. The system ranged from oligo- to mesotrophic state with moderate pollution levels (Carlson's Trophic State Index and Shannon's Index), indicating a reduction of the nutrient accumulation effects by the existing water renewal frequency. This study recommends incorporating qualitative and quantitative phytoplankton assessment in ecological monitoring of the stable coastal sites to prevent future harmful algal episodes.

Long-term study of phytoplankton dynamics in a supply reservoir reveals signs of trophic state shift linked to changes in hydrodynamics associated with flow management and extreme events.

This study analyses over a decade (2009-2022) of monitoring data to understand the impact of hydrological characteristics on water quality and phytoplankton dynamics in Prospect Reservoir, a critical water supply for Greater Sydney, Australia, known for its excellent water quality. Water quality and phytoplankton dynamics were related to hydrodynamics, linked to flow management and the water quality of inflows. Phytoplankton biovolume increased after a prolonged drawdown and subsequent refill event, mainly driven by dinoflagellates, and corresponded to increases in total phosphorus and water temperature. The hydrological period following the 2019/2020 summer bushfires (post-bushfire) that impacted connected reservoirs, was marked by increased flow activity and nutrient loading, leading to significant shifts in the phytoplankton community. Functional group classification and ordination analysis indicated a transition from taxa typically dominant in oligotrophic conditions to meso­eutrophic. This transition correlated with elevated nutrient levels and chlorophyll-a (Chl-a), and reduced Secchi depth and dissolved oxygen, providing evidence of eutrophication. Q index indicated good water quality post-bushfire, contrasting with a eutrophic status assessment using Chl-a. Our findings highlight the importance of analysing long-term datasets encompassing varied hydroclimatological conditions for a deeper understanding of reservoir behaviour. A comprehensive approach to water quality assessment is recommended, combining functional group classification, Q index and Chl-a measurements for effective reservoir health assessment. This research provides novel insights into the effects of disturbances such as bushfires, on water quality and phytoplankton dynamics in an underrepresented geographic region, offering valuable knowledge for managing water resources amidst growing climate variability.

Change of dominant phytoplankton groups in the eutrophic coastal sea due to atmospheric deposition.

Nutrient stoichiometry and input of trace metals may profoundly affect the growth and community structure of phytoplankton. A bioassay experiment was designed to explore the key components in atmospheric deposition that affect marine phytoplankton growth by adding aerosols and analogues nutrients and Cu to the surface water of the coastal East China Sea (ECS). Our results showed that atmospheric deposition along with the input of phosphate could largely enhance the chlorophyll a (Chl a) concentrations in this eutrophic water. Phosphorus addition lifted the proportions of T. oceanica in Diatoms and B. brevisulcata in Dinoflagellates. T. oceanica replaced S. costatum and became the dominant diatom species after the Chl a peak, probably associated with the N/P ratio approaching to 16. Atmospheric aerosols containing affluent N and little P showed limited promotion to Chl a, and the positive effect was very likely due to the soluble Cu and other trace metals supplied by the aerosol. Moreover, soluble aerosol Cu was found to be conducive to the relative abundance of most dominant class Coscinodiscophyceae, and both soluble aerosol Fe and Cu seemed to be very important for increasing the proportion of S. costatum. Soluble metals could be the key components in aerosols controlling the phytoplankton composition in the eutrophic sea and such impact might exceed affluent P provided by other exogenous sources.

Phytoplankton dynamics and renewable energy potential induced by the environmental conditions of Lake Burullus, Egypt.

The research evaluates the spatio-temporal phytoplankton community structure and abundance along with the pollution sources and the lake bioenergy potential, primarily in order to better understand the interplay of the environmental factors affecting them in inland coastal waters. Burullus Lake, located in the north of the Nile Delta of Egypt, is selected as a case study area. Field investigations along with sampling of lake water from 55 sites in the period 20-25 September 2020 are performed. The physicochemical analysis is carried out for the lake water bathymetry, temperature (T°C), pH, salinities (total dissolved solids (TDS) and electric conductivity), and nutrient contents (nitrate, nitrite, ammonia, and phosphate). Phytoplankton identification and biological analysis are used to document the taxa and abundance along with their contents of chlorophyll-a, protein, carbohydrates, and lipids. Then, the trophic index (TRIX), along with the total phytoplankton biomass and the energy potentials, is estimated. Statistical analyses were appraised for the univariate summary statistics, correlation analysis, regression analysis, multivariate statistical analysis including principal component analysis (PCA), and clustering techniques (both geographic position and the k-means clustering) which were conducted using the PAST 4.03 package. The geostatistical modeling of the ordinary kriging implemented in the ArcGIS 9.3 package was appraised for mapping the studied parameters. Results clarified ranges with wide variations for the water depth of 0.90-2 m (av. 130.5 cm), T°C of 26.6-30.20°C (av. 28.3 °C), alkaline pH of 7.78-8.92 (av. 8.6), and TDS of 0.3-17.09 (av. 4.33) gm/l. Ranges of nutrients (mg/l) are also widely varied with nitrates of 0.44-8.36 (av. 3.5), nitrites of 0.004-7.45 (av. 0.4), ammonia range of 0.03-8.54 (av. 1.4), and phosphate of 0.1-4.9 (av. 0.9). A much-diversified phytoplankton community showed maximum counts of 1005 × 103 units.l-1 to a minimum of 340 × 103 units.l-1 for a total of 145 taxa from 61 genera and six classes typically of freshwater forms. The largest biomass (3.06 × 10-3 kg/m3) and energy potential (19.87 × 10-3 kWh/kg) marked the downstream area of the Brimbal Canal, followed by the area located in front of the eastern Burullus and El-Gharbiya drains, which exhibited 2.76 × 10-3 kg/m3 and 17.96 × 10-3 kWh/kg, for the biomass and the energy potential, respectively. Geographic position and k-means clustering techniques distinguished three homogenous classes of marked intra-class variations. PCA analysis distinguished three principal components summed for about 95% of the variations. Intense environmental pollution at the drain downstream areas is indicated by many fish mortality occurrences that were related to the blooms of the toxic Microcystis aeruginosa among the cyanophyte species, and also due to the dominance of the Euglena spp. and Phacus spp. of the Euglenophyceae, which assimilate lots of organic matters in these areas. Lake water movement in the form of turbulent flows and mixing regimes is affected by wind direction and the amount of flows from the sea drains. The estuarine Nile canal has a great effect on the water's physicochemical properties, particularly the nutrient loads, inducing the phytoplankton composition and abundance, total biomass, and the biological contents hence the energy potential. Nutrient load from discharged water from drains was a major contributor to raising the total algae counts and their corresponding contents of the carbohydrates, lipids, proteins, and the chlorophyll-a, which arranged in decreasing order of influence. Phytoplankton dynamics are mostly linked to climatic, hydrologic fluctuation of the drain water flows, and hence, the associated nutrient load discharged from land use changes to fish farms and the related agricultural practices south of the lake. The adopted integrated analyses proved promising, which confirmed the combined effects of environmental factors on lake pollution and the bioenergy potentials.

Year-to-year variation in phytoplankton biomass in an anthropogenically polluted and complex estuary: A novel paradigm for river discharge influence.

We examined the effects of nutrient availability and turbidity on phytoplankton biomass over 9 years in Gwanyang Bay, Korea, which is an anthropogenically polluted and complex estuary. While dredging and reclamation shaped geochemical features, river discharge with low-turbidity water and sewage treatment plants contributed to nutrient loading. The replete levels of nutrients and short water-residence time suggest the inapplicability of the washout theory, whereas the presence of NH4+ suppressed the growth of phytoplankton. A reduction in the river discharge caused a concomitant decline in the loading and dilution of suspended particles. All these features led to an increase in SPM, light limitation, and NH4+ concentration. GLM estimates revealed negative effects of NH4+ and SPM on chlorophyll a over 9 years while SEM verified synergistic effects of NH4+ and SPM compared with positive effects of NO2 + NO3-. Our findings provide new insights into phytoplankton bloom dynamics in Gwangyang Bay.

Assessing in situ dominance pattern of phytoplankton classes by dominance analysis as a proxy for realized niches.

This study looks at two facets of dominant phytoplankton classes during phytoplankton succession. A detailed assessment of this issue is of special interest with regard to realized niches from a theoretical point of view but also for lake management as practical application. A realized niche mirrors the functional adaptability of an organism in a lake-specific constellation of environmental parameters. Therefore, the characterization of realized niches could be a key factor for management of problematic waters. Different strategies exist to control eutrophication and the risk of blooms by harmful algae. During the last decades, many restoration measures were initiated to manage eutrophicated inland lakes. In the past, it has become evident several times that restoration strategies do not necessarily lead to a reduction of biomass of undesirable cyanobacteria but can even promote their development. Due to this uncertainty of success and the high costs for remediation strategies, new prediction tools are required - ideally, based on routine monitoring data. Therefore, we developed a new method to extract potential optimal growth conditions (POGC) as indicators of realized niches for different phytoplankton taxa from existing data to improve existing strategies used in lake remediation and restoration. The analysis presented in this work is based on dominance pattern of different phytoplankton groups relative to environmental variables. Interpretation of these dominance patterns as indicators of POGC showed distinct pattern for several phytoplankton classes for all investigated objects. We identified low nitrogen and phosphate concentrations as favorable condition for cyanobacteria in Lake Auensee and Lake Feldberger Haussee. The reservoir Bleilochtalsperre showed a high N/P-concentration and cyanobacteria dominance was generally very low.

Reservoirs override seasonal variability of phytoplankton communities in a regulated Mediterranean river.

Water hydrology, temperature and transparency, as well as nutrient retention downstream of the reservoirs alter the temporal and spatial distribution patterns of phytoplankton communities in regulated rivers. The seasonal dynamics of phytoplankton communities in the Ebro was analysed in contrasting water flow periods in sections upstream and downstream of three large reservoirs, as well as in an intermediate site. Phytoplankton communities changed in response to seasonal variations in the areas not influenced by the reservoirs, but the phytoplankton distribution downstream of the reservoirs was driven by their particular hydrodynamics. The change in environmental conditions promoted by reservoirs influenced the pattern of replacement between diatoms and green algae of the upstream section. Differences in the phytoplankton community structure, abundance and environmental variables between upstream and downstream sites were maximal during low flow periods. Chlorophytes and dinoflagellates were present during low flow periods upstream of the reservoirs and in the intermediate site. Cocconeis cf. placentula characterized the downstream section, associated to the presence of macrophytes in that section. The present study sheds light on the consequences of river regulation under potential scenarios of climate change, and results could be used to anticipate ecological problems in large regulated rivers under these circumstances.

Phytoplankton dynamics in the Gulf of Aqaba (Eilat, Red Sea): a simulation study of mariculture effects.

The northern Gulf of Aqaba is an oligotrophic water body hosting valuable coral reefs. In the Gulf, phytoplankton dynamics are driven by an annual cycle of stratification and mixing. Superimposed on that fairly regular pattern was the establishment of a shallow-water fish-farm initiative that increased gradually until its activity was terminated in June 2008. Nutrient, water temperature, irradiation, phytoplankton data gathered in the area during the years 2007-2009, covering the peak of the fish-farm activity and its cessation, were analyzed by means of statistical analyses and ecological models of phytoplankton dynamics. Two datasets, one from an open water station and one next to the fish farms, were used. Results show that nutrient concentrations and, consequently, phytoplankton abundance and seasonal succession were radically altered by the pollution originating from the fish-farm in the sampling station closer to it, and also that the fish-farm might even have influenced the open water station.

Vitamin b(1) and b(12) uptake and cycling by plankton communities in coastal ecosystems.

While vitamin B(12) has recently been shown to co-limit the growth of coastal phytoplankton assemblages, the cycling of B-vitamins in coastal ecosystems is poorly understood as planktonic uptake rates of vitamins B(1) and B(12) have never been quantified in tandem in any aquatic ecosystem. The goal of this study was to establish the relationships between plankton community composition, carbon fixation, and B-vitamin assimilation in two contrasting estuarine systems. We show that, although B-vitamin concentrations were low (pM), vitamin concentrations and uptake rates were higher within a more eutrophic estuary and that vitamin B(12) uptake rates were significantly correlated with rates of primary production. Eutrophic sites hosted larger bacterial and picoplankton abundances with larger carbon normalized vitamin uptake rates. Although the >2 µm phytoplankton biomass was often dominated by groups with a high incidence of vitamin auxotrophy (dinoflagellates and diatoms), picoplankton (<2 µm) were always responsible for the majority of B(12)-vitamin uptake. Multiple lines of evidence suggest that heterotrophic bacteria were the primary users of vitamins among the picoplankton during this study. Nutrient/vitamin amendment experiments demonstrated that, in the Summer and Fall, vitamin B(12) occasionally limited or co-limited the accumulation of phytoplankton biomass together with nitrogen. Combined with prior studies, these findings suggest that picoplankton are the primary producers and users of B-vitamins in some coastal ecosystems and that rapid uptake of B-vitamins by heterotrophic bacteria may sometimes deprive larger phytoplankton of these micronutrients and thus influence phytoplankton species succession.

Variation of climatic and physical co-determinants of phytoplankton community in four nictemeral sampling days in a shallow tropical reservoir, Southeastern Brazil

Spatial and temporal variation of climatic and physical characteristics in a shallow tropical reservoir in the city of São Paulo, Southeastern Brazil, and their possible influence on the dynamics of the phytoplankton population. Samples were taken at 5 depths of the water column (subsurface: 1% Io, 10% Io, 2 m, and bottom) and at 4 hour intervals (6:00, 10:00, 14:00, 18:00, 22:00, 2:00, and 6:00 h) during summer (March 3-4), fall (June 13-14), winter (August 29-30), and spring (November 29-30) of 1994 at a single sampling station. Garças Reservoir (23º39'S, 46º37'W) is a kinetic turbulent system, highly influenced by winds, with stratification that may last for days or weeks, and which undergoes mixing periods more than once in a year. A thermal pattern of this type is comparable to the warm discontinuous polymictic. Considering its optical properties, the water body was classified as an ecosystem with moderate turbidity, which decreases basically due to increased phaeopigment concentration during the spring. Also, the reservoir is an ecosystem whose phytoplanktonic community is subjected to stress, the degree of which depends on level of light penetration.

Foram estudadas as variações espacial e temporal das características climáticas e físicas em um reservatório tropical raso situado na cidade de São Paulo e sua possível influência na dinâmica da comunidade fitoplanctônica. Foram retiradas amostras da coluna d'água (subsuperfície, 10% Io, 1% Io, 2 m e fundo) a intervalos de 4 horas (6, 10, 14, 18, 22, 2 e 6 h) durante o verão (3-4 de março), outono (13-14 de junho), inverno (29-30 de agosto) e primavera (29-30 de novembro) de 1994. Concluiu-se que o Reservatório das Garças (23º39'S, 46º37'W) é um sistema cinético turbulento, altamente influenciado pelo vento, com estratificações térmicas que podem durar dias ou semanas, sofrendo períodos de mistura mais de uma vez ao ano. O padrão térmico desse tipo é comparável ao polimítico quente descontínuo. Do ponto de vista de suas propriedades ópticas, o reservatório foi classificado como um ecossistema de turbidez moderada, que diminui basicamente pelo aumento na concentração de feopigmentos na primavera. O reservatório é um sistema sob estresse e a intensidade do estresse para a comunidade fitoplanctônica deve-se à pouca penetração de luz, a qual aumenta do verão para a primavera.